Motor-driven hammer



K. A. R. ERFASS MOTOR DRIVEN HAMMER Filed March 9, 19555 llllllllltnlhll s l. S l FSO V A ET YN mw Tg, VMM www@ ha( m f A WMW@ 1 M w Patented Dec. 17, 1935 UNITED sTATEs PATENT OFFICE MOTOR-DRIVEN HAMMER Karl Axel Ragnar Erfass, Stockholm, Sweden Application March 9, 1935, Serial No. 10,274 In Sweden July 23, 1934 7 Claims. (Cl. 125-33) My invention relates to an improvement in a sleeve in which the portion 6 of the striking hammers of the kind provided with a striking member is movable. Between the two parts 6, 'I member, which receives a reciprocating motion I provide a spring in such a manner that the from a motor in order to act upon a tool. In such striking body 'I hangs by the spring, when the hammers the connection of the striking memhammer is held in a vertical or inclined position. 5 ber with the motor shaft for transforming the The lower cylindrical sleeve shaped portion 9 rotation into a reciprocating motion generally surrounds a guide I@ for the tool and between the consists o1" a cross-head and a joint link extendsaid portion ii and the lower portion I5 of the ing from the said cross head to the piston-like hammer casing I provide a buffer spring II, striking member. Said member consists of two which prevents the part 'I from striking against 10 parts arranged one after the other in relation to the part Id in case the tool is removed from the the stroke, the outer part constituting the striksame. ing body proper. |Ihe said two parts are resili- According to my invention I arrange between ently connected with each other. the two parts (i, l of the striking member an air An object of my'invention is to arrange an space Io in the cylindrical portion 8, which space 15 air space in the connection between the said may be lled with air by air inlets I2, so that the two parts in such a manner that an air cushion upper part which forms a piston Ia moving is formed which in cooperation with the resilient in the said space will not act direct upon the connection considerably improves the actie-n of striking body l but only by means of the air cushthe hammer, as will be seen from the following. ion formed in the said air space. Losses of air,

Another object is to provide the said air space if any, in the space I6 are compensated for by with one or more air inlets, which are opened, air entering thro-ugh the air inlets I2, when the when the upper part of the striking member upper part 5 of the striking member has unmoves upward by means of its connection with covered the same for example by action of the the cross-head, but are closed when the said spring 5. part moves downward, the air being compressed In the piston @a there is an oil chamber I3, in the air space and transmitting the movement which by means of holes lli communicates with of the cuter part of the striking member. the faces of the two parts of the striking mem- A further object is to provide the hammers ber, which slide one within the other, so that with means to lubricate some faces of the two the said faces may be effectively lubricated. parts of the striking member, the said faces be- By the provision of the said air cushion the ing movable relatively to one another and slidspring due to the servo action of the air cushion,

ing one within the other, the inner part is promay be made comparatively weak, so that during vided with oil holes leading to the said faces, the subsequent working stroke of the striking which slide one within the other. body it may be easily stretched thereby increas- The invention is illustrated by way of an eming the elasticity thereof and making the length bodiment in the accompanying drawing, in which of the stroke greater than that of the connecting a hammer improved according to this invention is rod. In addition hereto a vibrationless recoil and shown in side view and partial section. a stronger blow is obtained as an essential fea- Figure l. shows a partial cross section of the ture of my hammer. embodiment in its entirety, To completely utilize the favorable action of Figure 2 shows a side View of a detail and the air cushion it is necessary to X the spring Figure 3 is a side view of a modication of the steadily to the part 6 and to the striking body same detail. l. In view hereof I have provided each of thenr Figure 4 is another side view of said modicawith a portion for lixing the spring, which is ef- 45 tion. fective as weil as simple. To explain this detail By means of a pinion Ia and a toothed ring Ib the said portion of the striking body for xing the motor I drives a cross-head 2, which by the spring is viewed from the side in Figure 2. means of a ball bearing Il is rotatably mounted The exterior of the striking body is provided in a holder 3 and by means of a link 1I provided with two flanges 29, ZI, which form a peripherie 50 with ball joints I3, I9 is connected with the upgroove 25 for the appertaining end winding of per or inner part 5 of the striking member. The the spring. Due to its own resilience the largest lower or outer part l of said member i. e. the strikpart of the said end winding is steadily disposed ing body proper is provided with cylindrical end in the groove but the winding continues through portions 8, 9. The upper portion 8 constitutes an opening 22 in the ange 20. Hence, the part 55 Cil of the spring, disposed in the groove, is located in a plane perpendicular to the axis of the striking body. After a bend 24 the spring extends spirally as usual. The spring contacts the striking body only near and in the groove, by which the striking body may move freely within the spring in its longitudinal direction but yet be steadily fixed to the spring. The xing portion 0f the part 6, i. e. at the opposite end of the spring, is made in the same way. The spring winding is introduced into its groove thereby that the spring, after having been put on the part 6 (or 1), is turned relatively to the said part in such. a manner that one end 23 of the flange 20 enters between the spring end and the next winding. It is then turned further until the spring end has passed almost around the part, i. e. until the bend 24 meets the ilange end 23.

The spring may also be iixed in Such a manner that in the portion surrounded by the spring windings at one or both ends of the spring there is a groove 215 (Figure 3) for one or more of the windings of the spring, the said groove, when seen from the entering end, extending some Way a spirally with the pitch of the spring and after that some way b in a plane perpendicular to the axis of the spiral. When the end winding of the spring is turned` in the last mentioned part b of the groove to a stop c (Figure fi), it will be steadily fixed in the groove because the groove direction deviates from' the regular spiral of the spring.

Naturally, I may use my invention also in other hammers than the one shown in the drawing.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In motor-driven hammers means for transforming a rotation motion into a reciprocating one and for transmitting said reciprocating ino-- tion to a striking membel two parts arranged one after the other in relation to the stroke and constituting said striking member, elastic means connecting said two parts to each other for obtaining a movement of the parts relation to each other, and the provision of a builer air cushion in the connection between the two parts, which constitute the striking member.

2. In motor-driven hammers means for transforming a rotation motion into a reciprocating one and for transmitting said reciprocating motion to a striking member, two parts arranged one after the other in relation to the stroke and constituting said striking member, elastic means connecting said two parts to each other, one of the parts forming a pump-cylinder and the other the appertaining piston, which is adapted to move along the path of the striking strokes, said cylinder containing air, which constitutes a buffer air cushion acting when the pump chamber is decreasing.

3. In motor-driven hammers means for transforming a rotation motion into a reciprocating one and for transmitting said reciprocating motion to a striking member, two parts arranged one after the other in relation to the stroke and constituting said striking member, elastic means connecting said two parts to each other, one of the parts forming a pump cylinder and the other the appertaining piston, which is adapted to move along the path of the striking strokes, said cylinder containing air, which constitutes a buffer air cushion acting when the pump chamber is decreasing, the provision of air inlets leading to the pump chamber containing the air cushion so as to make it possible to supply fresh air to be substituted for air which may have escaped.

4. In motor-driven hammers means for transforming a rotation motion into a reciprocating one and for transmitting said reciprocating motion to a striking member, two parts arranged oneafter the other in relation to the stroke and constituting said striking member, elastic means connecting said two parts to each other, one of the parts forming a pump cylinder and the other the appertaining piston, which is adapted to move along the path of the striking strokes, said cylinder containing air, which constitutes a buffer air cushion acting when the pump chamber is decreasing, the provision of oil intakes in those faces of the parts of the striking member, which slide one within the other, said intakes communicating with an oil chamber within the pump piston.

5. In motor-driven hammers as claimed in claim 1, in which the two parts of the striking member are united means of a screw spring, by which the striking body proper hangs the spring being connected to a cylindrical portion of one of the parte. at least, said portion being provided with a groove for at least the outermost spring winding, in which the said Winding is clamped by its own resilience in a plane perpendicular to the axis of the cylinder or the spiral.

6. In motor-driven hammers as claimed in claim 1, in whi member are united by means oi a screw spring, by which the striking body proper hangs the spring being connected to a cylindrical portion of one of the parts at least, said portion being provided with a groove for at least the outermost spring winding, in which the said winding is clamped by its own resilience in a plane perpendicular to the axis oi the cylinder or the spiral, the groove being peripherical and merging into a side opening through which the spring winding continues in its normal spiral where it has no contact with the cylindrical portion.

7. In motor-driven hammers means for transforming a rotation motion into a reciprocating one and for transmitting said reciprocating motion to a striking member, two parts arranged one after the other in relation to the stroke and constituting said striking member, a spring connecting the two parts to each other for obtaining a movement of the parts in relation to each other, at least one ofthe parts having a cylindrical portion provided with a groove for at least the outermost winding ot the spring, said groove running partly helically, partly peripherically so that the said winding is clamped by its own resilience in the groove.

KARL AXEL RAGNAR ERFASS.

the two parts of the striking 

